Objective To evaluate the gastric microbiome in patients with chronic superficial gastritis (CSG) and intestinal metaplasia (IM) and investigate the influence of Helicobacter pylori (H. pylori) on the gastric microbiome. Methods Gastric mucosa tissue samples were collected from 54 patients with CSG and IM, and the patients were classified into the following four groups based on the state of H. pylori infection and histology: H. pylori-negative CSG (n=24), H. pylori-positive CSG (n=14), H. pylori-negative IM (n=11), and H. pylori-positive IM (n=5). The gastric microbiome was analyzed by 16S rRNA gene sequencing. Results H. pylori strongly influenced the bacterial abundance and diversity regardless of CSG and IM. In H. pylori-positive subjects, the bacterial abundance and diversity were significantly lower than in H. pylori-negative subjects. The H. pylori-negative groups had similar bacterial composition and bacterial abundance. The H. pylori-positive groups also had similar bacterial composition but different bacterial relative abundance. The relative abundance of Neisseria, Streptococcus, Rothia, and Veillonella were richer in the I-HP group than in G-HP group, especially Neisseria (t=175.1, P<0.001). Conclusions The gastric microbial abundance and diversity are lower in H. pylori- infected patients regardless of CSG and IM. Compared to H. pylori-positive CSG group and H. pylori-positive IM, the relative abundance of Neisseria, Streptococcus, Rothia, and Veillonella is higher in H. pylori-positive patients with IM than in H. pylori-positive patients with CSG, especially Neisseria.